Lubricating oil composition, inhibitor therefor, and method of manufacturing the same



Tatented Dec. 24, 1 940 LUBRICATING 01L COMPOSITION, INHIBI- TOR THEREFOR, AND IMETHOD OF MANU- FACTURING THE SAME Troy Lee Cantrell and James Otho Turner, Lansdowne, Pa., assignors to Gulf Oil Corporation, Pittsburgh Pa., a corporation of Pennsylvania No Drawing. Application September 11, 1936, Serial No. 100,382

14 Claims. (Cl. 252-48) UNITED STATES PATENT OFFICE Our invention relates to lubricating oils and more particularly to lubricating oil compositions containing an oil-soluble agent ar agents effective to inhibit or mitigate the normal corrosive or destructive action of lubricating oil deterioration products upon certain types of bearing metals under certain conditions of use, said agent or agents also having the properties of imparting so-called extreme pressure" characteristics to the lubricating oil compositions, and also being effective to reduce or eliminate undesirable oxidation changes in the oil.

Despite the many technological advances made in the art of refining and applying lubricating oils and in the composition of bearing materials, modern lubricating oils and bearings often fail to perform satisfactorily. It is well known in the art that straight petroleum lubricants have fairly well defined limits of bearing speeds, pressures, and temperatures within which they will give acceptable service. These limitations are often exceeded in modern designs, resulting in machines that cannot be satisfactorily lubricated by straight mineral oils. These modern designs are justified by engineers in their efforts to provide machines to conform to the ever-increasing demand for compactness, speed, power and acceleration in modern engines. Many modern designs have already exceeded the above-mentioned limits wherein straight petroleum lubricating oils perform acceptably; therefore, it is necessary to provide Albricating compositions that extend and widen the limits formerly associated with straight lubricating oils.

Moreover, highly paraffinic oils having excellent vscosity-gravity constants, volatilities, carbon residue values, and resistance to sludging and oxidation; and hence of high value for use under relatively mild lubricating conditions, sometimes tend to be even less satisfactory than the less highly paraffinic oils, when the oridnary limits of temperature, pressure, and bearing speed are exceeded. This may be due in part to the fact that the deterioration products of paraflinic constituents are more active than those resulting from naphthenic or other nonparaffinic constituents, and it may be due also to the fact that the nonparaffinic constituents have some inhibiting effect upon either the deterioration of the paraffinic constituents or upon the behavior of products resulting from such deterioration, at high temperatures and pressures and in the presence of certain metals. However, the inhibiting value of the nonparaffinic constituents is low per unit concentration, and they are less satisfactory with respect to viscosity-gravity constant, carbon residue, and similar criteria of lubricating quality than the parafiinic constituents. A more satisfactory solution of the'problem would be to substitute for the nonparaflinic constituents removed in the more drastic refining treatments or absent because of the highly parafiinic nature of the original stock, some inhibiting or mitigating agent which would be far more effective per unit concentration and hence less detrimental with respect to the other physical properties which also affect the ultimate lubricating value of the oil.

Improved bearing metals have recently been developed which are mechanically advantageous under many operating conditions. These bearing metals include binary and ternary alloys of cadmium, silver, copper, lead, and nickel; as examples of such improved bearing metals frequently employed at the present time we may mention cadmium silver, cadmium silver-copper, cadmium-nickel-copper, and copper-lead alloys. However, such alloys are more subject to chemical attack than babbit and other bearing alloys used in the past, and their use at high temperatures, high speeds, and high pressures is sometimes accompanied by a deterioration of the oils employed for their lubrication, which in turn may destroy the bearings. The exact mechanism of this action is no doubt complicated and is perhaps not fully understood; it is quite possible that some of the metals present in the bearings tend to promote such deterioration, and that other metals present are subject to attack from the deterioration products. Whatever the cause or the mechanism, the result is that the combination of drastic lubricating conditions and alloy bearings of the general nature indicated frequently causes trouble; the bearings may be badly etched or corroded, and the quality of the oil may be rapidly deteriorated.

It has been observed in some cases that the more highly paraflinic oils are apt to cause more difiiculty in this respect than less paraifinic oils. It is highly desirable, therefore, to provide means whereby the oils may be so improved as to give satisfactory operating results under the conditions noted, and this is especially true insofar as concerns the more highly parafiinic oils, which should and do command a premium in price.

Moreover, it is well known that all hydrocarbon oils are more or less subject to changes through oxidation, resulting in undesirable deterioration, acid formation, and increase in carbon residue, viscosity, sludging, and the like. Such oxidative changes may become more rapid or more far-reaching in extent in the presence of metals such as those employed in modern bearings, for example those of the general class mentioned above.

In order to meet these problems and to provide more satisfactory lubrication under the conditions indicated, various improvement agents have been incorporated in hydrocarbon oils prior to their sale and use. Some of these are extremely efiective but too expensive for general use. Others, while having satisfactory inhibiting or mitigating characteristics, are unsatisfactory for other reasons. A primary requisite of any such improvement agent is good oil-solubility under service and marketing conditions; moreover, since solubilities vary in difierent types of oils, the improvement agent should be capable of being added in the requisite amount to oils of different characters.

The improvement agent should also be highly efiective per unit concentration in the lubricating oil compositions; otherwise it would'be necessary to add such an amount of the improvement agent as to substantially modify many of the desirable physical properties of the lubricating oil itself. The lubricating oils in which the improvement agents are incorporated have been carefully refined to meet exacting specifications, and if it is necessary to incorporate therein a 40 relatively large amount of some agent differing in physical properties from the oil itself, the re sulting composition may prove unsatisfactory for the very purposes for which the lubricating oil was prepared. In general, it is desirable that 45 the improvement agent should be effective at concentrations not exceeding one or two per cent by weight of the lubricating oil, although, as will be shown hereinafter, somewhat higher concentrations may occasionally be justified for special purposes.

.Among the more available comparatively inexpensive improvement agents which have been suggested and employed for this general purpose are various oil-soluble compounds of phosphorus, and especially trivalent phosphorus, for example aryl esters of phosphorous acid. Perhaps the specific agent which has been most largely used up to the present time is triphenyl phosphite. This compound is sufficiently inexpensive to make its use economic in certain instances, but it does not represent an entirely satisfactory solution of the problem, and, for certain oils at least and under certain conditions, its use is definitely unsatisfactory. Triphenyl phosphite, while having moderate lubricating properties, is much less viscous and oleaginous than the lubricating oils in which it is usually desired to incorporate an improvement agent, for example extreme-pressure lubricants and automotive lubricants. Moreover, its solubility in hydrocarbon oils is not extremely good and this is particularly the case insofar as concerns the more highly refined or more highly parafiinic lubricating oils; in many cases, as little as 0.1% of triphenyl phosphite 7 produces a definite haze or cloudiness immediately upon addition to hydrocarbon oils, and after remaining in the oil for a moderately extended period of time it may produce a definite sludging action, an action which becomes especially marked upon exposure to air or to sunlight or when the oil is packaged in metallic containers, such as cans made of tin plate, terne plate, and the like.

The inhibiting and mitigating properties of triphenyl phosphite with respect to corrosion of bearing metals of the class mentioned hereinbefore in many instances may be entirely satisfactory in themselves. But it will be obvious that if the oil has been deprived of the improvement agent prior to use, through sludging or precipitation, the eventual users of the oil may be deprived of this potential benefit. In addition to its poor solubility and tendency to sludge, triphenyl phosphite, when added to hydrocarbon oils which are subsequently packaged in metallic containers made of tin plate, terne plate or the like, tends to form deposits upon the surfaces of the metallic containers. Here again the problem happens to be more acute with respect to the more highly parafiinic oils, for the reason that such premium oils are generally and advantageously dispensed in sealed metallic containers rather than in bulk, and because any clouding, sludging, or depositing action is more detrimental with respect to the sale of these highly refined oils, of which an important advantage from the sales standpoint is their improved appearance and attractiveness to the eye.

The simpler aryl and alkyl phosphites and phosphates, such as triphenyl phosphite and tricresyl phosphate, contain phosphorus in relative ly high concentration, which fact tends in general to reduce the solubility of these compounds in hydrocarbon mixtures, especially in highly parailinic oils. It is also probable that this relatively high phosphorus content is responsible for their tendency to deposit out on metal surfaces at low temperatures.

Such phosphites leave much to be desired in respect to antioxidant properties; the aryl phosphates may even have no antioxidant efiect at all. The simple aryl phosphites, in particular, tend to hydrolyze in the presence of moisture, and may, as a result of this action, exert a pronounced corrosive effect upon iron; it will be obvious that such hydrolysis will tend to form highly corrosive aryl acids, such as phenol.

It is, therefore, an object of our invention to provide an improvement agent 'or inhibitor for addition to hydrocarbon lubricating oils, which agent shall be in the form of a compound containing both phosphorus and sulfur and having a satisfactory inhibiting or mitigating effect upon the destructive action of lubricating oils on alloy bearing surfaces under actual conditions of use where such destructive action would otherwise take place.

It is also an object of our invention to provide a mixture of an agent having an especially high corrosion-inhibiting or corrosion-mitigating effect with a second agent serving as a blending agent therefor and itself having desirable inhibiting and antioxidant properties.

It is also an object of our invention to provide an improvement agent or agents of the character indicated herein, having the property of imparting desirable extreme-pressure characteristics to hydrocarbon oils when incorporated therein.

Another object of our invention comprises the provision of an improvement agent or agents for addition to hydrocarbon oils, having desirable antioxidant and stabilizing properties, and effective to retard increase in viscosity, carbon residue, acidity, and sludging of both highly parafiinic and less highly parafiinic oils.

A further object of our invention is to provide improved lubricating compositions comprising hydrocarbon lubricating oils and certain improvement agents incorporated therein.

A still further object of our invention is to provide a method or methods of manufacturing improvement agents having desirable characteristics for addition to mineral oils.

Our invention has for further objects such additional operative advantages and improvements as may hereinafter be found to obtain.

In our co-pending application, Serial No. 99,- 662, filed September 5, 1936, we disclosed the use of inhibitors prepared by reacting phosphorus trichloride with certain antioxidants; said antioxidants comprising water-insoluble reaction products obtained by reacting phenols with olefins.

We have found that extremely effective improvement agents or inhibitors of the general character indicated can be prepared by reacting phosphorus pentasulfide (P285), or a mixture of phosphorus pentasulfide and phosphorus trichloride with antioxidants of the class indicated above; alternatively we may prepare our improve agent by reacting an antioxidant of the class indicated with phosphorus pentasulfide and blending the product with an agent prepared by treating such an antioxidant with phosphorus trichloride. Such antioxidants and methods of preparing the same are disclosed in the prior copending application of Stevens and Gruse, Serial No. 702,258, filed December 13, 1933 (nowU. S. Patent No. 2,061,111, patented Nov. 17, 1936), and in the co-pending applications of Troy L. Cantrell, Serial No. 64,413, filed February 1'7, 1936, and Serial No. 99.488, filed September 4, 1936, to which reference may be had for further details. The disclosures of the co-pending applications referred to constitute in effect apart of the disclosure of our present application, insofar as relates to the preparation of such antioxidant materials, which are used as starting materials in preparing phosphorus-containing improvement agents in accordance with our present invention.

Referring, for example, to the aforesaid copending application Serial No. 99,488, there is disclosed a process of manufacturing antioxidants wherein a phenol is mixed with from one to ten per cent of sulfuric acid having a strength of sixty to one hundred per cent, or even fuming sulfuric acid, and an olefin or a mixture of olefins is passed, preferably in the vaporous or gaseous phase, through the liquid mixture until the phenol undergoing reaction has gained in weight from to 200 per cent, or thereabouts, followed by washing the product so obtained with water and with caustic soda solution, the concentration of which does not exceed 15 per cent. Various phenols may be employed, for example phenol (CsHsOH) itself, the three cresols (CsH4OH-CH3) certain xylenols (CsHa-(CI-Is) 2-OH) and crude cresylic acids also may be employed. Where, in accordance with one aspect of our present invention, the antioxidant thus prepared is subsequently to be reacted with a mixture of phosphorus pentasulfide and phosphorus trichloride or with phosphorus trichloride alone, the phenolic starting materials should be as free as possible from pyridine bases; the presence of pyridine bases in the antioxidant product would result in undesirable reactions upon the subsequent treatment of the antioxidant with phosphorus trichloride. As olefinic material there may be employed individual olefins themselves, mixtures of olefins, or mixtures of olefinic and nonolefinic material. By way of example, the olefinic starting material may be butylenes, amylenes, refinery gases containing normally gaseous olefins (ethylene, propylene, butylene) in varying amounts, and cracked distillates or other relatively low-boiling hydrocarbon mixtures containing normally liquid olefins and in some instances also containing substantial amounts of dissolved normally gaseous olefins.

When the'reaction is conducted with the olefin in the gaseous phase, the product is relatively highly concentrated with respect to effective antioxidant material and may not require distillation or concentration for the purpose of isolating the latter. On the other hand, when the reaction is conducted with the olefinic material in liquid phase, and especially when the concentration of olefins in the starting material is comparatively low, the product may be relatively dilute with respect to the effective antioxidant material comprising for example a solution of such antioxidant in gasoline-like polymers or unreacted liquid hydrocarbons. In such case, the antioxidant material may be concentrated by distillation or otherwise as set forth in the abovementioned co-pending applications, prior to use in the process described herein.

The exact chemical and structural nature of the antioxidant materials, as thus prepared and employed as a starting material in the manufacture of our improved addition agents, is largely obscure. Although we have been able to identify certain types of compounds in these antioxidant materials, it will be realized that, especially since mixtures of various phenols and mixtures of various olefins are frequently employed in the manufacture of these antioxidants, the number of possible chemical compounds is large and varied. In general, they differ from the simple alkylated phenols in that they are insoluble in dilute caustic soda solution, and also in that they are good antioxidants and gum-inhibitors, whereas simple alkylated phenols are not. In general, also, the alkylations, in such instances as they occur, are of secondary and tertiary types; the methods set forth in the above co-pending applications do not produce normal or primary alkylation linkages. Alkylated phenols with normal or primary linkages are undesirable, due to fact that both such materials and their products of reaction with phosphorus pentasulfide tend to be relatively insoluble in high-gravity lubricating oils. (It may be noted that insofar as the general problem set forth hereinabove is concerned, the high-gravity oils are the principal offenders. Coastal and other low-gravity oils do not ordinarily require the addition of inhibitors, although their other lubricating properties may be and generally are less satisfactory than those of Pennsylvania and other highgravity oils.) It is possible that certain alkylated phenols of normal or primary linkage might be satisfactory provided the chains were long enough, say chains of four carbon atoms or more, on account of the closer resemblance in structure of such compounds to paraffinic lubricating oil constituents. However, this is doubtful and such compounds would be expected to be of prohibitive cost.

We have identified as constituents in the various antioxidant materials prepared as set forth hereinbefore such compounds as follows:

rtho-isopropyl phenol Ortho-tertiary butyl phenol 2, 4-ditertiary butyl phenol Ortho-isoamyl phenol Ortho-tertiary amyl phenol In addition to the above-listed compounds, similar derivatives of various homologues of mono-, di-, and polyhydroxy phenols may be present. It may be remarked, however, that while some of the constituents of such antioxidants may be identified, it is difficult or impossible to identify all of the constituents of any one antioxidant material of the character indicated and it is equally impossible to say which particular compound or type of compound may be the most important. As a matter of fact, we have not been able to isolate or identify any single constituent or to recover any fraction of the concentrated antioxidants prepared in accordance with the aforesaid Cantrell application, Serial No. 99,488, which constituent or fraction has an anti-oxidant value as high as that of the total concentrated product. Nor for the purpose of our present invention is it necessary so to do; the fact remains that antioxidants may be prepared in the manner set forth hereinbefore and in the aforesaid co-pending applications, and such materials comprise suitable starting materials for the manufacture of phosphorus-containing improvement agents or inhibitors in accordance with our present invention; certain of the constituents of the antioxidant starting material which are not in themselves effective as antioxidants are nevertheless capable of being converted by reaction with phosphorus pentasulfide, phosphorus trichloride, or a mixture of these compounds to phosphorus-containing materials useful as inhibitors.

As aforesaid, we prepare our improved addition agents or inhibitors by reacting antioxidants of the general character described hereinabove with phosphorus pentasulfide alone or with a solution of phosphorus pentasulfide in phosphorus trichloride. Where the reagent consists of phosphorus pentasulfide alone, the general procedure is as follows: The antioxidant material, which should preferably be dry, is warmed to reduce its viscosity, and powdered phosphorus pentasulfide is slowly added in predetermined amount, the mixture being stirred as the addition proceeds. The temperature is then raised to 300 -400 F., or thereabouts, and maintained at this elevated temperature for a suitable time in order to drive off hydrogen sulfide resulting from the reaction. The mixture is then cooled. The product thus prepared may be filtered to remove insoluble impurities by means of a mechanical filter, or if it is desired to lighten the color of the material, it may be filtered through suitable decolorizing clay such as fullers earth, charcoal, or acid-treated clay. Wherever the inhibitor material as initially prepared is of relatively high viscosity, it may be diluted with a suitable hydrocarbon liquid of lower viscosity in preparation for the filtration step. By way of example, we may employ a light naphtha as a diluent; the use of naphtha has the advantage that such naphtha may be readily removed after the filtration operation, by distillation. Or, we may employ as diluent a low-viscosity lubricating oil similar to the oil to which the inhibitor is to be added eventually; in such case it is unnecessary to remove the diluent prior to incor- 5 porating the inhibitor in the lubricating oil.

Where the reagent comprises a solution or suspension of phosphorus pentasulfide in phosphorus trichloride, the same general procedure is employed, except that in this case the reagent is added as a liquid.

The amount of reagent added will vary over a considerable range, depending upon the desired characteristics of the final product. Where the antioxidant starting material is relatively highly concentrated and phosphorus pentasulfide is added in sumcient amount to react with all of the antioxidant present, the products in general possess very high inhibiting powers but tend to be extremely viscous and insufficiently soluble in highly parafiinic oils. They may, however, be employed in preparing improved extremepressure lubricant compositions, greases, and other heavy lubricants. For example, Where the antioxidant material has initially been prepared by reacting olefins comprising primarily hydrocarbons containing four carbon atoms per molecule and phenol (CsHsOH) itself, and such antioxidant materials in concentrated form are fully reacted with phosphorus pentasulfide, the final products will contain in the neighborhood of 9 per cent by weight of sulfur and 4.5 per cent by weight of phosphorus. Such products, when added to hydrocarbon oils, have only a mild antioxidant effect but are extremely effective to 85 inhibit or mitigate corrosion of the character indicated hereinbefore. 7

While we may, as we have indicated, introduce a suflicient amount of phosphorus pentasulfide to obtain completion of reaction with all of the antioxidant, we ordinarily find it desirable to limit the amount of phosphorus pentasulfide added, so that the final product represents a mixture of the phosphorus-containing inhibitor and some of the original antioxidant material 5 and is less viscous and is more soluble. Products thus prepared are more soluble in highly parafiinic oils and while still highly effective as inhibitors also have high antioxidant value. The products thus prepared, especially if they have been heated to around 400 F. or higher during preparation, tend to have ratios of sulfur to phosphorus lower than 2:1; for example a little more than 1:1, through loss of sulfur occurring during preparation.

By reacting antioxidant material of the character indicated fully and then blending back the product with additional antioxidant, we may obtain useful products, in which the ratio of sulfur to phosphorus is roughly 1:2; such products are highly effective antioxidants as well as inhibitors, and do not have the same specific properties as products obtained by merely reacting the antioxidant with phosphorus pentasulfide to a limited extent.

We have found that highly advantageous results are obtained by reacting the antioxidant starting material with a mixture of phosphorus pentasulfide and phosphorus trichloride. The proportions and total amounts of these reagents will depend upon the concentration and chemical nature of the original antioxidant material and upon the desired amounts and proportions of phosphorus and sulfur in the ultimate products. The effect of this is to increase the ratio of phosphorus to sulfur in the final products, as compared with the approximate 1:2 ratio obtained with phosphorus pentasulfide alone as a reagent and where the antioxidant is fully reacted.

This procedure may be varied by reacting one portion of the antioxidant material fully with phosphorus pentasulfide, and reacting another portion with phosphorus trichloride in the manner described in our co-pending application, Serial No. 99,662, filed September 5, 1936, and blending the two products in the desired proportions.

Whether either of the two last-mentioned procedures are followed, there is ultimately obtained a mixture of the phosphorus pentasulfide reaction product with phosphorus trichloride reaction product, as well as, where desired, more or less unreacted antioxidant material. This type of product has special advantages; for one thing the phosphorus trichloride reaction products are in general more soluble in paraffin oils than those obtained with phosphorus pentasulfide, and act as blending agents for the latter. Furthermore, without desiring to limit our invention to any particular theory of action, it may, nevertheless, be observed that in general oil-soluble compounds containing trivalent phosphorus become effective as inhibitors at somewhat lower temperatures than is true of similar compounds containing pentavalent phosphorus. Our mixtures of the type referred to in the foregoing paragraph, containing the phosphorus pentasulfide reaction product (in which the phosphorus is in pentavalent form) along with phosphorus trichloride reaction product (in which phosphorus is present in trivalent form), therefore, tend in general to have wider ranges of effectiveness as inhibitors than would be true if the phosphorus were present entirely in trivalent form or entirely in pentavalent form. Moreover, the phosphorus trichloride reaction product possesses higher antioxidant value than the phosphorus pentasulfide reaction product. It may also be true that the phosphorus pentasulfide reaction product has a stabilizing effect upon the phosphorus trichloride reaction product, this stabilizing effect being particularly noticeable under conditions where the phosphorus trichloride reaction product would otherwise tend to be decomposed or otherwise reduced in effectiveness prior to the time when the inhibiting effect is required; the factors underlying these efiects are extremely complex, but regardless of what the explanation may be, we have observed that mixtures of these two classes of inhibitors are effective over a wider range of operating conditions than is true of either class of inhibitors alone.

With reference to the mixed compounds and partial reaction products mentioned above, we have found it advantageous for many purposes to regulate the proportions of the reagent or reagents used, or to regulate the proportions of the blends, in order to obtain as final products inhibitors containing not more than about 10 per cent of sulfur and phosphorus combined, assuming the antioxidant starting material to be sub stantially free from diluents. For example, such an inhibitor could contain as much as 5 per cent of sulfur and 5 per cent of phosphorus, an increase in either percentage being preferably balanced by a corresponding decrease in the other. Higher total sulfur-plus-phosphorus percentages tend to indicate insufficient solubilities of the products in the highly paraffinic oils for which inhibitors are most needed. Where the products are used in conjunction with suitable blending agents, however, this limitation is less important from the standpoint of solubility. We have found it advantageous to keep the phosphorus content of the concentrated inhibitors between 1 and 5 per cent; products containing more phosphorus than this tend to be too active at atmospheric temperatures, especially in contact with metals. The sulfur content should vary between about 1 and 10 per cent.

We prefer to employ as starting materials antioxidants, prepared as set forth above and in the aforesaid co-pending applications, and having physical properties within the following range:-

Gravity: API 15.0 to 25.0

Specific gravity: 60/60 F 0.9659 to 0.9042

Viscosity, SUV at F.: sec 150 to (solid) Color Water white to 7 (NPA) Pour point (liquids only) F 0 to 30 Melting point (solids only) F 80 to 225 Our invention, in its broadest aspects, however, is not limited to the preferred starting material mentioned hereinabove but contemplates the manufacture of inhibitors of the general class described from any alkylated phenols so long as such alkylated phenols possess definite antioxidant properties, are insoluble in water, insoluble or only slightly soluble in dilute alkali, and are permanently soluble up to 5 per cent in paraffin oils. For example, we may employ as starting materials antioxidants prepared by reacting various light cracked hydrocarbon distillates and other normally liquid olefinic hydrocarbon mixtures, with phenol in the presence of sulfuric acid, as described in the aforesaid co-pending applications. It is a requisite of such olefin-phenol reaction products, however, insofar as the present process is concerned, that one or more secondary and/or tertiary carbon linkages be present in the compound.

The antioxidant value of this starting material should be such that the addition of 0.01 per cent by weight thereof to standard gasoline stock hav ing an oxygen stability test (E. G. C. Method) of, say, minutes, will raise the oxygen stability to at least 240 minutes. Less potent antioxidants are unsuitable as starting materials.

The character of the final phosphorus-containing inhibitor will of course vary with the character of the phenolic and olefinic material employed in the manufacture of the antioxidant starting material, with the extent of the absorption of the olefin, and with the amount of phosphorus subsequently introduced. All of these factors are however very intimately inter-related. These are the primary factors, but it will be obvious that there are numerous secondary factors, for example the degree of purification and decolorization of the antioxidant starting material.

Naturally, it is to be expected that the viscosities, specific gravities and other physical characteristics of the panticular phenols employed have a corresponding effect upon the product, to some extent at least; this effect may, however not always, hold true where the degree of olefin absorption varies over comparatively wide limits and where the percentages of sulfur and phosphorus in the final compound also vary.

When cresylic acid, ortho-cresol and metacresol and the like are used in the manufacture of the antioxidant, we prefer to limit the olefin absorption to around one mol per mol of the phenolic material, i. e. to give a water-insoluble product representing roughly 135 to 150 per cent by volume of the original phenol, in order ultimately to secure inhibitors that are sulficiently soluble in the higher gravity oils; the result of carrying the absorption of olefin farther is to make the antioxidant product less capable of absorbing the desired amount of phosphorus in the final stage.

When the antioxidant starting material is prepared from phenol (CeHsOH) itself, e. g. per cent phenol," the degree of absorption of olefin may be carried farther, for example to about two mols of olefin per mol of phenol (based on the assumption that the olefin is made up entirely of C4 hydrocarbons).

The preferred olefins are those containing from three to eight carbon atoms per molecule; the higher the molecular weight of the olefin, the more viscous the final phosphorus-containing product will be. Olefins containing more than eight carbon atoms per molecule tend to reduce the phosphorus content of the final inhibitor product. Ethylene (CzI-Ir) on the other hand, is insufiiciently reactive, requiring the use of fuming sulfuric acid and does not sumciently reduce the acidity of the original phenol.

The best olefin starting materials are those containing from three to five carbon atoms per molecule, especially butylenes; fractions obtained from gases produced in the pyrolysis of hydrocarbon oils and rich in olefins of this approximate range represent advantageous and available raw materials.

After the reaction between the phenol and olefin has been carried to the desired degree of completion, the product is washed with water and dilute caustic soda in the manner set forth hereinabove and in the aforesaid co-pending applications. The resultant water-insoluble antioxidant material is then preferably dried. The drying may be accomplished by filtering this material through adsorbent clay or the like, the effect of which is to dehydrate and decolorize. Or, the drying may be accomplished by heating the antioxidant material to about 400 F. in suitable apparatus; this procedure dehydrates and tends to darken the antioxidant material.

The dry antioxidant may then be treated directly with the phosphorus reagent, or it may first be distilled to separate undesirable low-- boiling and high-boiling constituents, respectively. Thus we may distill under a vacuum of from 11 in. to 28 in. Hg, to recover a fraction distilling over between 400 and 550 R, which fraction may then be treated with phosphorus pentasulfide. The lower boiling material, and sometimes also the residue, may be recycled for further reaction with olefins in the presence of sulfuric acid, or used as an antioxidant.

The following examples will serve to illustrate our invention insome of its more specific embodiments.

EXAMPLE 1 (a) Preparation of antioxidant starting material 50 gal. of 90 per cent phenol were mixed with 20 lb. of 98 per cent black acid, the latter being a recovered acid obtained from acid sludge produced in washing hydrocarbon oil with sulfuric acid. The 90 per cent phenol employed had the following properties:

Specific gravity: 60/60 F 1.050 Melting point, capillary tube: F 91.9 Color: NPA 5 The phenol was placed in a suitable iron vessel and heated to a temperature of F. Olefinic gas was then introduced slowly to agitate the phenol and the acid was added in two batches, 10 lb. at first and the remaining 10 lb. two hours later. The temperature at the end of two hours was 150 F. and the mixture was maintained at this temperature for 16 hours, olefinic gas being passed through the mixture during this time at the rate of 1600 cu. ft. per hour. The operation was conducted under a pressure of from 15 to 25 lb. per sq. in.

The olefinic gas employed in this example was a cracked hydrocarbon gas fraction obtained in the pyrolysis of hydrocarbon oil, and having a specific gravity of 1.785. Upon agitation of a sample of this gas with 64 per cent sulfuric acid, the acid absorbed 12.5 per cent by volume of the gas, which may be considered as isobutylene and dienes. The remainder of the sample lost 20 per cent by volume (based on the original volume of gas) by absorption in 87 per cent acid, which may be considered as propylenes, butylenes and similar constituents. The remainder of the sample, upon being washed with bromine water, following the two acid washes, lost 2.6 per cent by volume (based on the original volume of gas), which may be considered as ethylene. The gas, therefore, contained 34.1 per cent by volume of unsaturated constituents.

Upon completion of the operation, there was produced a material representing 300 per cent by volume of the original phenol, i. e. 150 gallons.

The crude product was then raised from 200 to 212 F., and 20 gal. of 10 per cent caustic soda solution were added to neutralize the sulfuric acid present. .The resultant product, after removal of the caustic layer, was washed with boiling water, live steam being introduced during the washing operation, and was then allowed to settle for two hours after which the aqueous layer was withdrawn. The remaining material was blown with air for two hours in order to reduce the moisture content of the product to two per cent by weight.

The final product, produced as set forth hereinabove, had a volume of gal. and comprised a mixture of about 90 per cent of an oil-soluble material having antioxidant properties, and about 10 per cent of what appear to be gasoline-like polymers. It is a highly satisfactory antioxidant and gum inhibitor. Typical physical properties of products as thus prepared are as follows:

Gravity: API 21.6 Viscosity, SUV at .100 F.: seconds 122 Color: NPA Dark Pour point: F 0

(1)) Preparation of final inhibitor To 85 parts by weight of antioxidant material prepared as described above, and previously dried, 15 parts by weight of phosphorus pentasulfide were slowly added, the temperature meanwhile being raised to about 300 R, where it was maintained for several hours after the addition of the reagent until no further evolution of hydrogen 75 sulfide was apparent. The reaction product was then cooled and had the following properties:

Gravity: API 3.0 Viscosity, SUV at 210 F.: seconds 86.5 Color, NPA Dark Phosphorus: per cent by wt 4.44 Sulfur: per cent by wt 9.07

This product is, as will be clear from the properties listed above, a very thick and viscous material and is of limited solubility in parafiinic oil; additions of only 0.5 per cent or even less of this material to a highly parafiinic oil may impart a hazy or cloudy appearance to the oil. However, as will be made clear herein, this product may be blended with some of the original antioxidant material or with a reaction product obtained by treating such antioxidant material with phosphorus trichloride, and the blends thus prepared are readily soluble in highly paraifinic oils.

EXAMPLE 2 (a) Preparation of antioxidant starting material In this example the antioxidant starting material was prepared in the same manner as that described in connection with Example 1.

(b) Preparation of final inhibitor 92.5 parts by weight of this antioxidant material were treated with 7.5 per cent by weight of phosphorus pentasulfide, the operating procedure being similar to that described in connection with Example 1. The resulting material had the following properties:

Gravity: API 6.4 Viscosity, SUV at 100 F.: seconds 4226 Color, NPA Dark Phosphorus: per cent by weight 3.83 Sulfur: per cent by wt 4.57

This product is much less viscous than that produced in accordance with Example 1, and is suificiently soluble in highly para-flinic oils to be used alone as an inhibiting agent therefor.

EXAMPLE 3 (a) Preparation of antioxidant starting material In this example antioxidant material prepared in the same manner as that described in connection with Example 1, was distilled under a moderate vacuum, the fraction distilling over at vapor temperatures between 300 and 550 F., being segregated from the lighter distillate and residue. Typical physical properties of a fraction collected in this manner were as follows:

Gravity: API 16.8 Viscosity, SUV at 100 F.: seconds 185 Color, NPA 13 (1)) Preparation of final inhibitor 87 parts by weight of a fraction of antioxidant material prepared as described hereinabove were treated with a mixture of 13 parts by weight of phosphorus trichloride and 5 parts by weight of phosphorus pent-asulfide. The operating procedure was similar to that described above. The

resulting material had the following properties:

Gravity: API 5.3

Viscosity, SUV at 100 F.: seconds 1174 Color, NPA 4.0

Phosphorus: per cent by wt 3.95

Sulfur: per cent by wt 3.0

EXAMPLE 4 82.5 parts by Weight of an antioxidant fraction similar to that used in Example 3 were treated with 17.5 parts by weight of phosphorus trichloride, the procedure following that given in our co-pending application, Serial No. 99,662. The product had the following properties:

Gravity: API 10.3 Viscosity, SUV at 210 F 64.9 Color, NPA 2.25 Phosphorus: per cent by wt 3.57

The final inhibitor product was prepared by mixing 50 parts by weight of this material with 50 parts by weight of an inhibitor prepared as in Example 1, giving a blended inhibitor having the following properties:

Gravity: API 7.8 Viscosity, SUV at 100 F 1150 Color, NPA 3.5 Phosphorus: Percent by wt 3.76 Sulfur: Percent by wt 1.5

The products prepared in accordance with our invention, and as exemplified by those given in the foregoing examples, are all excellent inhibitors, and when added to lubricating oils, especially highly paraffinic oils, in amounts up to about 1 per cent by weight of the oil give improved and advantageous lubricating compositions.

All of these inhibitors strongly inhibit corrosion of metal alloy bearings such as those of silver, cadmium, copper and nickel under conditions where the oil alone would cause such corrosion. On the other hand, these inhibitors are stable at ordinary temperatures and do not tend to deposit out of the lubricating oil compositions on metal surfaces such as those of terne plate, tin plate and the like when packaged and stored prior to sale and use. The inhibitors prepared in accordance with Examples 2, 3, and 4 are all permanently soluble in hydrocarbon oils of high paraffinicity and do not tend to settle out nor form sludge under ordinary conditions of storage and use. Moreover, these inhibitors all have excellent antioxidant properties, the antioxidant properties rising in proportion to the amount of unreacted antioxidant starting material remaining in or blended into the final product. These inhibitors, as well as inhibitors prepared in accordance with Example 1, are not subject to hydrolysis to any detrimental extent; the products of such hydrolysis as may occur are in themselves antioxidant and non-corrosive materials.

In actual use, oil compositions containing our inhibitors tend to diminish in sulfur content, a circumstance which may be accomplished by liberation of sulfur in some form, probably as hydrogen sulfide. However, this is not detrimental and may in fact be advantageous.

In preparing these materials we regulate the character and molecular weight of the phenolic starting material and the olefinic starting material respectively, the degree of olefin absorption in the phenolic reaction mixture and the relative amounts and proportions of phosphorus pentasulfide or phosphorus trichloride and phosphorus pentasulfide in accordance with the final concentration and proportions of phosphorus and sulfur desired in the final product. This regulation makes it possible to secure inhibitors having desired temperature responsiveness, activity, solubility, viscosity and color varying over a wide range. It is one of the advantages of our invention that we are able to produce a wide range of materials varying but slightly from each other with respect to both chemical and physical properties; such flexibility is difiicult o-r unsatisfactory with respect to simple aryl phosphites and also with respect to some alkylated phenols, especially those having normal alkylation linkages.

Wherever the expression highly paraflinic oil" is employed herein and in the claims hereinafter made it is in general intended to indicate lubricating oils conforming in physical properties to oils prepared from Pennsylvania crudes; these highly paraflinic oils are either oils derived from Pennsylvania crudes or oils which have been refined or blended to approach or even exceed the latter oils in parafiinicity. Where var ious materials are referred to as being soluble in such paraflinic oils, this expression is intended to mean that such materials may be incorporated into such oils in amounts up to ten per cent, without producing any haziness nor cloudiness in the appearance of the resultant compositions, at least under atmospheric temperatures and under the ordinary conditions to which such oil compositions are subjected in storage and handling prior to their actual use as lubricants.

A further advantage of our process and product is that the principal ingredients employed in the manufacture of the final product, namely olefins, are cheap and available to the refiner.

The following tables will serve to illustrate the effectiveness of our inhibitors and the value of lubricating compositions containing them:

Table I Oil with Untreated inhibitor oil (prepared as in Example 1) Makeup: Percent by weight:

Lubricating oil (10 SAE) 99. 9 Inhibitor 0. 1 General properties:

Gravity: API 32. 5 32. 5 Specific gravity: 60l60 0.8628 0.8628 Viscosit SUV- 100 F 183. 6 184 F 100. 2 210 F 46. 0 46. 5 Viscosity index. 107 107 V-G constant 0. 804 0. 804 Flash, 00 F. 410 410 Fire, 00: F 470 475 Pour point: F. +5 Color, N PA 1. 75 Sulfur: Percent.- 0.12 Phosphorus: Percent.... 0.01 Special oxidation and corrosion test:

Time oxidized: hr 48 48 Oil bath temperature: F. 347 347 Air rate: cc. per hr..- 2000 2000 Oil volume: cc 300 300 Cadmium-silver bearing:

Weight before test: g 37. 1883 36. 3790 Weight after test: g. 36. 4931 36. 3807 Change in weight: g -0. 6952 +0. 0017 Appearance Etched Good Table II Oil containing Untreated inhibitor oil prepared as in Example 2 Make-up, percent by vol Lubricating oil... 100 99. 5 Triphenyl phosphi 0. 5 Genera properties:

ravity: API 32.5 32. 2 Specific gravity: 60/60 F 0.828 0.8644 Viscosity, SUV

100 F 183. 6 184 130 F 100. 2 210 F 46. 0 46. l Viscosity index 107 107 V-G constant. 0. 804 0. 806 Flash, 00: F 410 410 Fire, 00: F 470 470 Pour point: F. 0 +5 Color, NPA 1.5 1. 75 Carbon residue: Percent. 0.03 0. 06 Appearance Clear Clear Almen test:

Journal speed: RPM 600 60 Rubbing speed: Ft. per min. 40 40 Lever load: Lb 10 16 Torque: Lb. ft. 10. 13 15 Unit load: Lb. sp. in 5000 8000 Lubricant temperature, F.--

Initial 86 82 Final 113 112 Special oxidation and corrosion test:

Time oxidized: Hr 48 48 Oil bath temperature: F. 347 347 Air rate: Co. per hr 2000 2000 Oxidized oil: Cc"--. 300 300 Gravity: API 30. 7 32. 1 Viscosity, SUV: Seconds- 0. 54 0. 1 l. 0 0. 4 Cadmium-nickel bearing shell:

Weight before test 37. 1883 36. 7025 Weight after test 36. 4931 36. 6895 Weight change 0. 6952 0. 0130 Appearance Badly etched Good Table III Oil with inhibg itor (prepared as in Example3) Make-up: Percent by wt.:

Lubricating oil 100 99. 1 Inhibitor 0.9 General properties:

Gravity: .API 32. 5 1 Specific gravity: 60l60 F 0.8628 Viscosity, S

100 F 186 181. 2 210 46.1 45.6 Viscosity 1ndex. 104 107 V-G constant- 0. 804 0. 807 Flash, 00: F 410 400 Fire, 00: F 465 470 Pour point: F 0 6 Color, NPA 1. 5 1. 75 Carbon residue: Percen 0. 05 0. 10 Special oxidation and corrosion test:

Time oxidized: hr 48 48 Oil bath temperature: F 347 347 Air rate: cc. per hr 000 2000 Oil volume: cc 300 300 Cadmium-silver Weight before test: g 37. 2149 36. 3653 Weight after test: g 36. 9665 36. 4302 Change in weight: --0. 2484 +0. 0649 Bearing appearance Etched Good The lubricating oil referred to in the tests listed in the tables given herein was an SAE 10 oil which had previously been treated with aluminum chloride.

The Special oxidation and corrosion test referred to in the foregoing tables is conducted as follows: An alloy bearing shell of certain commonly used standard dimensions is submerged in 300 cc. of the oil or oil composition in a 400 cc. Pyrex beaker and heated in a thermostatically controlled oil bath to C. (347 F.), and air, at the rate of 2000 cc. per hour. is bubbled through the oil in contact with the bearing shell.

At the end of 48 and 96 hours, the loss of weight and the condition of the bearing shell are determined, the bearing shell being washed free of oil and dried before weighing. When determining the effectiveness of various improvement agents, the usual procedure is to run a blank test simultaneously with the oil composition being tested, employing for that purpose a sample of the untreated oil.

In this test it is advantageous to employ commercial bearing shells. These shells comprise a suitable metal backing faced with the alloy bearing metal. In this way, the actual bearing face is subjected to severe deteriorative conditions. By comparison of the results of such tests with actual service tests, we have found them to be in substantial agreement as to the suitability of particular lubricants.

In the tests given in Tables I and III we employed so-called silver-cadmium bearings of the following approximate composition:

Metal Percent Cadmium .i 98 Silver 1 Copper 1 In the tests given in Table II, we employed so-called cadmium-nickel bearings of standard make, containing cadmium, nickel and copper.

In these tests the loss in weight, while not extremely high when expressed as per cent loss, is nevertheless very significant, as the bearing shells used have an alloy facing of only 0.008 to 0.012 in. thickness on a highly resistant backing and the observed losses in the reported tests often represent a loss of the order of ten per cent of the alloy facing.

In order to demonstrate the effectiveness of our improved inhibitors, we have carried out actual motor tests on a standard automobile engine equipped, for the purposes of these tests, with cadmium-silver and copper-nickel-lead bearings. In these tests, a good grade of motor oil, without inhibitor, caused bearing failures after having been run for the equivalent of from one thousand to two thousand miles, at speeds around fifty miles'per hour, and under loads of around fifty brake horse power. The same oil when protected by the addition of from 0.5 to 1.0 per cent by weight of our improved inhibitors, gave no evidence of serious attack on the bearings after being driven under the same conditions for the equivalent of around five thousand miles. After these tests with our improved lubricating compositions, the appearance of the bearings was only 'such as would normally be expected, assuming the entire absence of corrosion.

Our improved lubricating compositions, in these tests, showed results full comparable with those obtained by the use of lubricating oil containing triphenyl phosphite as an inhibitor; however, the other disadvantages inherent in the use of triphenyl phosphite and referred to hereinabove are avoided by the use of the inhibitors prepared as set forth hereinabove.

Various modifications in the operating procedure mentioned hereinabove will suggest themselves to those skilled in the art. For example, we have described washing the phenol-olefin reaction product with water and dilute caustic soda solution to effect neutralization and removal of the acid or acids (e. g. sulfuric acid and sulfonic acids) remaining in the reaction mixture after the introduction of the olefins has been discontinued. Such neutralization and removal may be effected in other ways, as by extraction with aqueous alcohol, contact with solid alkalis such as lime or sodium carbonate, or by contacting the reaction mixture with solid adsorbents such as fullers earth, activated carbon, or the like.

While we have described our invention hereinabove with reference to various preferred forms and embodiments, and with reference to various specific examples, it will be understood that our invention is not limited to the details of such illustrative embodiments or examples but may be variously practiced and embodied within the scope of the claims hereinafter made. Moreover, while we have in certain instances specifically given certain preferred ranges and proportions, it will be understood that our invention is not limited thereto and that such preferred ranges and proportions are in general selected for particular products and particular purposes; variations in proportions and in the methods of preparation result in products of different characteristics, such products having individual advantages and utilities.

What we claim is:

1. The method of preparing an oil-soluble organic phosphorus compound suitable as an improvement agent for hydrocarbon oils, which comprises reacting phosphorus pentasulfide with a water-insoluble reaction product of a phenol and an olefin having antioxidant properties when added to a hydrocarbon oil, the reaction being carried to such extent as to incorporate suflicient phosphorus and sulfur into the final product to give the final product the property of inhibiting the corrosion of bearing metals by hydrocarbon oils, when added to such oil, while retaining to a substantial extent the antioxidant value of the aforesaid phenol-olefin reaction product.

2. The method of preparing an oil-soluble organic phosphorus compound suitable as an improvement agent for hydrocarbon oils, which comprises passing a gaseous olefin into contact with a phenol in the presence of sulfuric acid until the reacting mixture has increased in volume from 30 to 250 per cent on the original phenol, washing the resultant antioxidant prod not with water and dilute alkali, and reacting at least a portion of the washed antioxidant product with phosphorus pentasulfide to obtain a final oil-soluble material containing not more than about per cent of phosphorus.

3. The method of preparing an oil-soluble organic phosphorus compound suitable as an improvement agent for hydrocarbon oils, which comprises passing a gaseous olefin into contact with a phenol in the presence of a catalyst until the phenol has absorbed from one to two mols of olefin per mol of phenol, washing the resultant antioxidant product with water and dilute alkali, and reacting at least a portion of the washed antioxidant product with phosphorus pentasulfide.

4. A method of lubricating bearing surfaces which comprises maintaining between bearing surfaces, one of which is an alloy of the class consisting of binary and ternary alloys of cadmium, silver, nickel, copper and lead, a film of lubricating oil which initially produces an effective lubricating action but which would normally tend to corrode the aforesaid alloy, and maintaining the effectiveness of the lubricating oil by incorporating therein a thiophosphate ester of a water-insoluble compound selected from the class consisting of secondary and tertiary alkylated phenols in a small but sufilcient proportion substantially to reduce the corrosion.

5. The method of preparing oil-soluble organic compounds suitable as improvement agents for highly paraffinic lubricating oils which comprises reacting an olefin and a phenol in the presence of a catalyst, Washing the resultant product with water and dilute alkali, treating at least a portion of the product with phosphorus pentasulfide, and regulating the degree of adsorption of olefin in the initial reaction stage with reference to the specific chemical character of the phenol and olefin, to secure an intermediate waterinsoluble product which, when treated in the subsequent reaction stage with phosphorus pentasulfide in the required amount to introduce from one to five per cent of phosphorus into the aforesaid intermediate product, will yield a sulfur-containing and phosphorus-containing product soluble in highly parafiinic oil.

6. The method of preparing an oil-soluble organic compound suitable as an improvement agent for highly parafiinic lubricating oils, which comprises reacting an olefin and a phenol in the presence of sulfuric acid, washing the resultant product with water and dilute alkali, treating a portion of the product with phosphorus pentasulfide and treating a second portion with phosphorus trichloride, and blending the resultant phosphorus-containing products to obtain a final produce soluble in highly parafilnic oil and containing a total of not more than about 10 per cent of combined sulfur and phosphorus.

'7. The method of preparing an oil-soluble organic phosphorus compound suitable as an improvement agent for hydrocarbon oils, which comprises reacting an olefin and a phenol in the presence of sulfuric acid, and treating at least a portion of the resultant product with a mixture of phosphorus pentasulfide and phosphorus trichloride.

8. Themethod of preparing an oil-soluble organic phosphorus compound suitable as an improvement agent for hydrocarbon oils, which comprises reacting an olefin and a phenol in the presence of sulfuric acid, and treating at least a portion of the resultant product with a mixture of phosphorus pentasulfide and phosphorus trichloride to obtain a final inhibitor product containing a total of from about 2 to 10 per cent of combined sulfur and phosphorus.

9. The method of preparing an oil-soluble organic phosphorus compound suitable as an improvement agent for hydrocarbon oils, which comprises reacting a mixture of phosphorus pentasulfide and phosphorus trichloride with a water-insoluble reaction product of a phenol and an olefin, said reaction product having antioxidant properties when added to a hydrocarbon oil.

10. The method of preparing an oil-soluble organic phosphorus compound suitable as an improvement agent for hydrocarbon oils, which comprises reacting phosphorus pentasulfide and phosphorus trichloride with water-insoluble reaction products of phenolic and olefinic material, said reaction products having antioxidant properties when added to hydrocarbon oil, the reaction being carried to such extent as to incorporate suflicient phosphorous and sulfur into the final product to give the final product the property of inhibiting corrosion of bearing metals by hydrocarbon oil, when added to such oil, while retaining to a substantial extent the antioxidant value of the aforesaid phenol-olefin reaction product.

11. A method of lubricating bearing surfaces which comprises maintaining between bearing surfaces, one of which is an alloy of the class consisting of binary and ternary alloys of cadmium, silver, nickel, copper and lead, a film of lubricating oil which initially produces an efiective lubrieating action but which would normally tend to corrode the aforesaid alloy, and maintaining the effectiveness of the lubricating oil by incorporating therein a mixture of a phosphite ester and a thiophosphate ester of a water-insoluble compound selected from the class consisting of secondary and tertiary alkylated phenols in small but suflicient proportion substantially to reduce the corrosion.

12. The method of preparing an oil-soluble organic compound suitable as an improvement agent for highly paraflinic lubricating oils which comprises reacting an olefin and a phenol in the presence of a catalyst, washing the resultant product with water and dilute alkali, treating at least a portion of the product with phosphorus trichloride and phosphorus pentasulfide, and regulating the degree of absorption of olefin in the initial reaction stage and the relative amounts and proportions of the phosphorus-containing reagents employed in the treating stage to secure an oil-soluble final product containing a total of from 2 to 10 per cent of combined sulfur and phosphorus.

13. An improvement agent for hydrocarbon lubricating oils comprising a thiophosphate ester of an anti-oxidant reaction product of an olefin and a phenol, the said ester retaining to a substantial extent the anti-oxidant value of said reaction product.

14. A lubricant composition comprising a major amount of a mineral oil and a minor amount of a thiophosphate ester of an anti-oxidant reaction product of an olefin and a phenol, the said ester retaining to a substantial extent the anti-oxidant value of said reaction product, and the said ester being present in suflicient amount to substantially retard the corrosive effect of the oil alone on hearing metal alloys.

TROY LEE CANTRELL. JAMES OTHO TURNER. 

